Function declaration syntax in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a function named greet.

Swift

func [1]() {
    print("Hello!")
}

Drag options to blanks, or click blank then click option'

Agreet

BsayHello

Chello

DprintGreeting

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than requested.

Forgetting to write the function name after func.

The function name should be greet as specified.

2fill in blank

medium

Complete the code to declare a function named add that takes two Int parameters.

Swift

func add(_ a: Int, _ b: Int) -> Int {
    return a [1] b
}

Drag options to blanks, or click blank then click option'

A/

B-

C*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Forgetting to return the result.

The function should add the two parameters, so the operator is +.

3fill in blank

hard

Fix the error in the function declaration to correctly return a String.

Swift

func welcomeMessage(name: String) -> [1] {
    return "Welcome, \(name)!"
}

Drag options to blanks, or click blank then click option'

AString

BBool

CInt

DVoid

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong return type like Int or Bool.

Forgetting to specify the return type.

The function returns a greeting message, which is a String.

4fill in blank

hard

Fill both blanks to declare a function that takes a Double and returns its square as Double.

Swift

func square(number: [1]) -> [2] {
    return number * number
}

Drag options to blanks, or click blank then click option'

ADouble

BInt

CString

DBool

Attempts:

3 left

💡 Hint

Common Mistakes

Using different types for parameter and return value.

Using Int instead of Double.

The parameter and return type are both Double because the function squares a Double number.

5fill in blank

hard

Fill all three blanks to declare a function that returns a dictionary with keys as uppercase strings and values as their lengths for words longer than 3 letters.

Swift

func wordLengths(words: [String]) -> [String: Int] {
    return words.filter { $0.count [3] 3 }.reduce(into: [String: Int]()) { result, word in result[[1]] = [2] }
}

Drag options to blanks, or click blank then click option'

Aword.uppercased()

Bword.count

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase words as keys.

Using wrong comparison operators.

Mixing up keys and values.

The function creates a dictionary with uppercase words as keys and their lengths as values, filtering words longer than 3 letters.

Practice

1. Which keyword is used to declare a function in Swift?

easy

A. def

B. func

C. function

D. method

Solution

1. Step 1: Recall Swift function declaration

   In Swift, functions always start with the keyword func.

2. Step 2: Compare options

   Only func uses func, the correct keyword for Swift functions.

3. Final Answer:

   func -> Option B

4. Quick Check:

   Swift functions start with func [OK]

Hint: Remember: Swift functions always start with 'func' keyword [OK]

Common Mistakes:

• Using 'function' instead of 'func'
• Confusing Swift with Python's 'def'
• Using 'method' which is not a keyword

2. Which of the following is the correct syntax to declare a function named greet that takes no parameters and returns nothing?

easy

A. func greet() -> void {}

B. function greet() {}

C. func greet {}

D. func greet() {}

Solution

1. Step 1: Check function declaration syntax

   In Swift, a function with no parameters and no return type is declared as func name() {}.

2. Step 2: Analyze each option

   func greet() {} matches the correct syntax. function greet() {} uses 'function' which is invalid. func greet {} misses parentheses. func greet() -> void {} uses 'void' which is not used in Swift.

3. Final Answer:

   func greet() {} -> Option D

4. Quick Check:

   Empty parameter list needs () and no return type means no arrow [OK]

Hint: Empty parameters always need () after function name [OK]

Common Mistakes:

• Omitting parentheses for parameters
• Using 'function' instead of 'func'
• Using 'void' as return type in Swift

3. What will be the output of the following Swift code?

func add(a: Int, b: Int) -> Int {
    return a + b
}

print(add(a: 3, b: 4))

medium

A. a + b

B. 34

C. 7

D. Error: Missing return statement

Solution

1. Step 1: Understand function parameters and return

   The function add takes two integers and returns their sum.

2. Step 2: Calculate the function call result

   Calling add(a: 3, b: 4) returns 3 + 4 = 7, which is printed.

3. Final Answer:

   7 -> Option C

4. Quick Check:

   Sum of 3 and 4 is 7 [OK]

Hint: Add numbers inside function and print result [OK]

Common Mistakes:

• Concatenating numbers as strings
• Forgetting to return a value
• Misunderstanding parameter labels

4. Identify the error in the following Swift function declaration:

func multiply(a: Int, b Int) -> Int {
    return a * b
}

medium

A. Missing colon between parameter name and type for b

B. Missing return keyword

C. Function name is invalid

D. Return type should be String

Solution

1. Step 1: Check parameter syntax

   Each parameter must have a colon between its name and type. Here, b Int is missing a colon.

2. Step 2: Confirm other parts are correct

   The return keyword is present, function name is valid, and return type Int is appropriate.

3. Final Answer:

   Missing colon between parameter name and type for b -> Option A

4. Quick Check:

   Parameters need colon between name and type [OK]

Hint: Check colons between parameter names and types [OK]

Common Mistakes:

• Omitting colon in parameter list
• Forgetting return keyword
• Using wrong return type

5. You want to declare a Swift function named describePerson that takes a String parameter name and an Int parameter age, and returns a String describing the person like "Name is Age years old." Which is the correct function declaration?

hard

A. func describePerson(name: String, age: Int) -> String {
return "\(name) is \(age) years old."
}

B. func describePerson(name String, age Int) -> String {
return "\(name) is \(age) years old."
}

C. func describePerson(name: String, age: Int) {
print("\(name) is \(age) years old.")
}

D. func describePerson(name: String, age: Int) -> Void {
return "\(name) is \(age) years old."
}

Solution

1. Step 1: Check parameter syntax and return type

   Parameters must have colons between name and type. The function returns a String, so return type must be String.

2. Step 2: Verify function body matches return type

   func describePerson(name: String, age: Int) -> String { return "\(name) is \(age) years old." } returns a String with correct string interpolation. func describePerson(name String, age Int) -> String { return "\(name) is \(age) years old." } misses colons. func describePerson(name: String, age: Int) { print("\(name) is \(age) years old.") } has no return type and uses print instead of return. func describePerson(name: String, age: Int) -> Void { return "\(name) is \(age) years old." } uses Void return type but returns a String, which is invalid.

3. Final Answer:

   func describePerson(name: String, age: Int) -> String { return "\(name) is \(age) years old." } -> Option A

4. Quick Check:

   Correct parameters and return type with string interpolation [OK]

Hint: Use colons for parameters and match return type with returned value [OK]

Common Mistakes:

• Omitting colons in parameters
• Using print instead of return for returning values
• Mismatching return type and returned value